The musical's choreographer tells THR of getting starstruck by the 'Stranger Things' cast, mapping Fallon's "raunchy waltz" with Justin Timberlake and often being confused with the 'This Is Us' actress of the same name.

From the very beginning, the Golden Globes were all about La La Land. Sunday night's awards show kicked off with an elaborate pre-taped musical number that was a recreation of the Lionsgate film’s opening song-and-dance, as host Jimmy Fallon navigated a red-carpet traffic jam with Lion’s Nicole Kidman, Game of Thrones’ Kit Harington, the cast of Stranger Things and Courtney B. Vance, Sterling K. Brown, John Travolta and Sarah Paulson of The People v. O.J. Simpson. Some cameos were made in character — Westworld’s Evan Rachel Wood powered down in her blue dress, while the hooded Rami Malek of Mr. Robot hacked the Tonight Show host’s hard drive — while others paid tribute to their roles, as Arrival’s Amy Adams was backed by dancers in HAZMAT suits.

How did the sunny, star-studded segment come together? “It was a bit of a scramble to get everyone cast, but if Jimmy Fallon calls, it’s like, ‘Of course,’” La La Land choreographer Mandy Moore tells The Hollywood Reporter of mapping the five-minute cold open, which was written and directed by The Tonight Show’s Dan Opsal and shot by the film's steadicam operator Ari Robbins.

Preparations first began just before Christmas, and the cameos were captured over three days just before the Globes (complete with a rain contingency plan, thanks to the week’s unpredictable weather). “We basically shot it in little vignettes, whenever the celebrities were available,” Moore explains, as each of the stars stopped by the Universal lot for nearly 30 minutes at a time and either recorded their audio component just before or after their shoot. “We didn’t have them for a long time, so I knew whatever they did had to be simple, effective and fun, but also gave them enough room to be their own personality.”

The segment also featured 27 of the Damien Chazelle film’s 30 dancers — this time, wearing costumes referencing the year’s popular titles. “Dan wanted to be true to the shots in the film, which were so fun to revisit and recreate,” says Moore. While Harington's appearance was shot earlier in London, the most exciting cameos on set were those by Travolta — “He was so lovely and immediately knew we wanted him to do the most iconic dance move ever known to mankind” — and the Stranger Things cast. Says Moore of watching Millie Bobby Brown, “She felt the pressure with that rap; it’s a lot of work. But everyone was so hyped and screaming behind the monitor. That was the first one we shot, and it set the tone for the entire thing.”

While the gridlock scene was shot during the day, Friday night was spent on a soundstage with Fallon and Justin Timberlake for what Opsal called “a hysterical, raunchy waltz.” Recalls Moore of spoofing Ryan Gosling and Emma Stone’s cosmo-set duet, “I just thought of the five most ridiculous moves that’d be great as a silhouette. They immediately went for it.”

That opening began what became La La Land’s big night, as the musical nabbed seven awards — a new record for any film at the Golden Globes. But it also was an illuminating moment for many viewers who might have confused the choreographer with the other notable Mandy Moore, the actress-singer on NBC's This Is Us.

“This mix-up has been going on for 15 years,” laughed Moore, a fan of the This Is Us star. “I thought it was so funny that right after Damien and Emma thanked me in their speeches, Mandy Moore came out to present — it was the climax of all of it! Someone tweeted at both of us, and we both wrote back that, finally, everyone’s getting that we’re two different people. I haven’t been able to meet her yet, but I look forward to finally doing so and laughing off all of this ridiculousness.”